It's not a meth lab people. They probably have the lab in the basement.
It's a hydroponic marijuana growing setup.
The lights are on at night for obvious reasons. The hose from the bathroom is to keep the water going. In such a large system you would need large water pumps to mvoe the water. To keep it quiet, you use the pressure from the municipal city supply.
They were worried about the power, because if the lights go off, the plants will most likely die if not tended too quickly.
Ask him for some, send it to me.